Aliens from a neighboring star system visited and educated the authors of the Bible.

The authors of the Bible used basic science to figure it out.

The authors of the Bible made a good guess.

Without further information, the best tentative conclusion is likely either #3 or #4, as the most likely explanations. To say that it's #1 is literally picking the most unlikely explanation out of the list.

Defense of Biblical Text

The Hebrew language is extremely reputed for being one that engages images and metaphors reflecting the basic beliefs of the day. All of the above quoted texts save Matthew (the only listed text that doesn't explicitly allude to a flat earth) are cited from Biblical poetry, which would easily engage the reader's cultural and contextual scientific knowledge concerning the vast reach of God's influence, power, etc. The bottom line, however, is that the Bible isn't a scientific text and was written by men inspired by God,, not written by God himself (as the Koran is said to derive providence from, etc); this allows for scientific errors that engage the readers on their own contextual level and communicate an idea, not a scientific truth.